Question

Describe the pathophysiology of atherosclerosis and how it causes myocardial infarction

Answer 1

Atherosclerosis is characterised by marked narrowing of the arteries due to plaque deposition. The atheromatous plaque is made up of cholesterol, fat, calcium and other constituents of blood. Atherosclerosis results in impaired circulation of blood to the area supplied by the affected artery.

Pathogenesis :

Atherosclerosis is a slow degrading process. The plaque develops slowly due to abnormal reaction of endothelial with blood components.

Variety of events take place in atheromatous plaque formation. The endothelium dysfunction results from variety of risk factors like diabetes, smoking, obesity, hypertension, hyperlipidemia.

The endothelium reacts with monocytes present in blood evoking inflammatory response and platelet aggregation.

The toxin irritants produced results in increased endothelial permeability to lipids. The LDL accumulates at the endothelium and gets oxidised due to ROS and macrophages.

Oxidised LDL stimulates inflammatory process by activating cytokines. The macrophages engulf the oxidised LDL resulting in foam cell production. This activates more cytokines aggravating inflammatory response.

Foam cells, activated platelets and cytokines results in thickening of the arterial wall. Calcification and fibrosis through proliferation of smooth muscle cell over the lesion occurs slowly resulting in narrowing of arterial lumen.

If the atherosclerosis develops in the coronary arteries that supply oxygen rich blood to cardiac muscles it can result in impaired blood supply to heart. This cause pain, angina, breathing difficulty and dysrhythmias. Continued impaired blood supply to heart results in myocardial ischaemia due to lack of oxygen to cells. If ischemia to cardiac muscles persists it results in tissue death as the cells cannot carry the basic metabolic functions due to lack of oxygen. This cardiac tissue death is known as myocardial infarction.